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  <a href="http://sudopedia.enjoysudoku.com/Uniqueness_Test.html#Uniqueness_Test_4">Uniqueness Test 4</a>
   <p>
   The <b>{7} cells {3}</b> form a unique {0} with two common <b>candidates {1} and {2}</b>.
   There are two possibilities to place the two digits into the {7} cells which leads to an invalid puzzle with two solutions.
   This <a href="http://sudopedia.enjoysudoku.com/Deadly_Pattern.html">deadly pattern</a> must be avoided because a valid puzzle can have just one solution.
   To avoid the deadly pattern extra candidates in one or several of the {7} cells exist to eliminate other candidates in the puzzle. 
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	<b>Digit {1}</b> can go only into one of the two <b>cells {4} and {5}</b> in the highlighted <b>{6}</b>.
	The other of the two <b>cells {4} and {5}</b> must contain one of the highlighted extra candidates to avoid the deadly pattern.</b>
	Therefore neither <b>{4} nor {5}</b> contains <b>digit {2}</b>.
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